Cohesion is the ability for atoms to stick, or bond, with like atoms to form bigger molecules of that atom. An example of this is one H2O molecule bonding to with many other H2O molecules in order to for just a drop of water. Cohesion is important because all atoms are coherent. If atoms suddenly stopped cohering, everything in the world would just vaporize.4 Adhesion is the ability of dissimilar molecules to cling together due to attractive forces, like the Van der Waals Forces. This is just another type of way for molecules to bond. When two molecules spin, their positive and negative side are constantly being exposed to each other. Therefore the two are attracted to each other because opposites attract.7 There are many different forms of adhesion also. One form of adhesion is not chemistry related; it is mechanical adhesion. That is when materials are use to stick things together like glue and Velcro and tape.4 Another type of adhesion is chemical bonding. Chemical bonding occurs when two compounds adhere by ionic bonding or covalent bonding. Ionic bonding occurs when one or more electrons from one atom are removed and attached to another atom, which results in positively and negatively charged ions9. A covalent bond is a bond where one or more pairs of electrons are shared by two atoms9. There is also electrostatic adhesion. This is when things adhere through static electricity, specifically adhesion between two substances or surfaces due to the presence of opposite charges, which attract each other10. Dispersive adhesion is another form of adhesion that occurs when two materials are held together by Van der Waals forces, the attraction between molecules that have positively and negatively charged ends11. Capillary action is a display of adhesion. This is the movement of liquid through thin tubes or porous media. Surface tension pulls the liquid column up until there is a sufficient mass of liquid for gravity to overcome the intermolecular forces. An example of capillary action in porous media is water being soaked up in a paper towel.3 Recently there have been new developments in the field of adhesion. Dr, Paul Steen, Professor at Cornell, has developed a device that can possibly have human walking on wall in the near future. This process involves adhesion through the surface tension of water. He forces a tiny bit of water out of tiny holes in a device he invented called the electroosmotic droplet switch. The surface tension that results is strong enough to hold only a few pounds now. This is reversible so you can get the two adhering item unstuck. So basically you can turn the adhesion “off”. Since the process is driven by electricity, he can just shut off the power source which reverses the process. The water is just absorbed back through the tiny holes through capillary action. I ended up coming up with a lab that would be used more of as a demonstration than a proof. I will apply a silicone to a glass sample and pour water on it. Then I will apply butter to a glass sample and pour water on it. Then I will have a glass sample I will do nothing to and pour water on it. With these three samples I will see which one prevents adherence the most. Then after I do that I will research how silicones prevent water from adhering and why they make water bead up.
Procedure
In my experiment I used a towel as a spread in which I did my experiment on top of, Blue Bonnet, Rain-X which was the silicone, a beaker of water, a dropper, a beaker of ice water, a Bunsen burner, and glass samples. First I laid the towel flat across the counter. Then I cleaned the glass samples. Then I put the glass samples out. I applied the Rain-X and the Blue Bonnet to two different glass samples and I left another sample alone. Then I dropped a few drops of water on each sample. After that I took pictures of the results. Then I cleaned up because time was running short. The next day I got my beaker of water and put ice cubes in it and measured the temperature and then I heated another beaker of water over the Bunsen burner. I then cleaned three glass samples and applied Rain-X to the three glass samples I just cleaned. Then I added a few drops of cold water to one glass sample. Then I turned off the Bunsen burner and measured the temperature then I added a few drops of hot water to a glass sample. Then I turned the Bunsen burner back on and let the water boil and I got the temperature of the boiling water. Then I added a few drops of the boiling water to a glass sample.
Results
When I added room temperature water to the glass sample with Rain-X, beaded up perfectly. There was barely any adhesion present. When I added water to the glass sample with Blue Bonnet on it, the water went all over the glass. It didn’t bead up at all. When I dropped water on the glass sample with nothing on it the water did the same thing as it did in the sample with the Blue Bonnet but I expected it to happen like that here. When I did this experiment with temperature I didn’t get to take pictures. The first glass sample had ice cold water on it. The temperature of the water was 1°C. When I dropped the water on the Rain-X, the water still beaded up. The next glass sample was the sample that I heated up then turned the burner off. The temperature of that water was 85°C. When I added the water there it still worked, meaning the water beaded up. The last glass sample was 100°C. When I added the water here the silicone, Rain-X, worked as if it was non-existent, meaning it didn’t bead up at all.
Conclusions
So if you are using Rain-X it should always work unless the rain in boiling when it falls. Silicone is a substance that is composed of both organic and inorganic polymers. They are usually heat resistant and hydrophobic, which means they don’t like water. They are hydrophobic because they are non-polar. The lack of polarity in the silicones is what makes the water not adhere to its surface.13 Water beads up because it has a high surface tension. It has a high surface tension because the two Hydrogen atoms are on one side and the Oxygen atom is on the other side. Since the Hydrogen is slightly positive and the Oxygen side is slightly negative, there will always be an attraction between water molecules, a force known as cohesion. When water comes in contact with a non-polar surface, the water beads in a spherical shape. It does this to get the most water possible while using as little surface area as possible. In a way this is the most efficient way.
Table of Contents
The Chemistry of Adhesion
Clifford
Introduction
Cohesion is the ability for atoms to stick, or bond, with like atoms to form bigger molecules of that atom. An example of this is one H2O molecule bonding to with many other H2O molecules in order to for just a drop of water. Cohesion is important because all atoms are coherent. If atoms suddenly stopped cohering, everything in the world would just vaporize.4 Adhesion is the ability of dissimilar molecules to cling together due to attractive forces, like the Van der Waals Forces. This is just another type of way for molecules to bond. When two molecules spin, their positive and negative side are constantly being exposed to each other. Therefore the two are attracted to each other because opposites attract.7 There are many different forms of adhesion also. One form of adhesion is not chemistry related; it is mechanical adhesion. That is when materials are use to stick things together like glue and Velcro and tape.4 Another type of adhesion is chemical bonding. Chemical bonding occurs when two compounds adhere by ionic bonding or covalent bonding. Ionic bonding occurs when one or more electrons from one atom are removed and attached to another atom, which results in positively and negatively charged ions9. A covalent bond is a bond where one or more pairs of electrons are shared by two atoms9. There is also electrostatic adhesion. This is when things adhere through static electricity, specifically adhesion between two substances or surfaces due to the presence of opposite charges, which attract each other10. Dispersive adhesion is another form of adhesion that occurs when two materials are held together by Van der Waals forces, the attraction between molecules that have positively and negatively charged ends11. Capillary action is a display of adhesion. This is the movement of liquid through thin tubes or porous media. Surface tension pulls the liquid column up until there is a sufficient mass of liquid for gravity to overcome the intermolecular forces. An example of capillary action in porous media is water being soaked up in a paper towel.3 Recently there have been new developments in the field of adhesion. Dr, Paul Steen, Professor at Cornell, has developed a device that can possibly have human walking on wall in the near future. This process involves adhesion through the surface tension of water. He forces a tiny bit of water out of tiny holes in a device he invented called the electroosmotic droplet switch. The surface tension that results is strong enough to hold only a few pounds now. This is reversible so you can get the two adhering item unstuck. So basically you can turn the adhesion “off”. Since the process is driven by electricity, he can just shut off the power source which reverses the process. The water is just absorbed back through the tiny holes through capillary action. I ended up coming up with a lab that would be used more of as a demonstration than a proof. I will apply a silicone to a glass sample and pour water on it. Then I will apply butter to a glass sample and pour water on it. Then I will have a glass sample I will do nothing to and pour water on it. With these three samples I will see which one prevents adherence the most. Then after I do that I will research how silicones prevent water from adhering and why they make water bead up.
Procedure
In my experiment I used a towel as a spread in which I did my experiment on top of, Blue Bonnet, Rain-X which was the silicone, a beaker of water, a dropper, a beaker of ice water, a Bunsen burner, and glass samples. First I laid the towel flat across the counter. Then I cleaned the glass samples. Then I put the glass samples out. I applied the Rain-X and the Blue Bonnet to two different glass samples and I left another sample alone. Then I dropped a few drops of water on each sample. After that I took pictures of the results. Then I cleaned up because time was running short. The next day I got my beaker of water and put ice cubes in it and measured the temperature and then I heated another beaker of water over the Bunsen burner. I then cleaned three glass samples and applied Rain-X to the three glass samples I just cleaned. Then I added a few drops of cold water to one glass sample. Then I turned off the Bunsen burner and measured the temperature then I added a few drops of hot water to a glass sample. Then I turned the Bunsen burner back on and let the water boil and I got the temperature of the boiling water. Then I added a few drops of the boiling water to a glass sample.
Results
When I added room temperature water to the glass sample with Rain-X, beaded up perfectly. There was barely any adhesion present. When I added water to the glass sample with Blue Bonnet on it, the water went all over the glass. It didn’t bead up at all. When I dropped water on the glass sample with nothing on it the water did the same thing as it did in the sample with the Blue Bonnet but I expected it to happen like that here. When I did this experiment with temperature I didn’t get to take pictures. The first glass sample had ice cold water on it. The temperature of the water was 1°C. When I dropped the water on the Rain-X, the water still beaded up. The next glass sample was the sample that I heated up then turned the burner off. The temperature of that water was 85°C. When I added the water there it still worked, meaning the water beaded up. The last glass sample was 100°C. When I added the water here the silicone, Rain-X, worked as if it was non-existent, meaning it didn’t bead up at all.
Conclusions
So if you are using Rain-X it should always work unless the rain in boiling when it falls. Silicone is a substance that is composed of both organic and inorganic polymers. They are usually heat resistant and hydrophobic, which means they don’t like water. They are hydrophobic because they are non-polar. The lack of polarity in the silicones is what makes the water not adhere to its surface.13 Water beads up because it has a high surface tension. It has a high surface tension because the two Hydrogen atoms are on one side and the Oxygen atom is on the other side. Since the Hydrogen is slightly positive and the Oxygen side is slightly negative, there will always be an attraction between water molecules, a force known as cohesion. When water comes in contact with a non-polar surface, the water beads in a spherical shape. It does this to get the most water possible while using as little surface area as possible. In a way this is the most efficient way.
References
1.“Adhesion.” Wikipedia. N.p., n.d. Web. 6 Mar. 2010. .
2. “Adhesive Bond Strong Enough to Hold a Human.” US News and World Report. N.p., 25 Feb. 2010. Web. 21 Mar. 2010. .
3. “Capillay Action.” Wikipedia. N.p., n.d. Web. 6 Mar. 2010. ..
4. “Cohesion (Chemistry).” Wikipedia. N.p., n.d. Web. 6 Mar. 2010. .
5. “Dispersive Adhesion.” Wikipedia. N.p., n.d. Web. 6 Mar. 2010. .
6. Kendall, Kevin. “Adhesion: Molecules and Mechanics.” Science 263.5154 (1994): 1720-1725. JSTOR. Web. 6 Mar. 2010. <http://www.jstor.org>.
7. “Van der Waals force.” Wikipedia. N.p., n.d. Web. 6 Mar. 2010. . .
8. "Water Surface Tension Creates New Adhesive Devise."Web.29.Mar.2010
9. "Chemical Bonds." Test Page for Apache Installation. Web. 29 Apr. 2010. ..
10. //"Electricalebook.com - Electrical Definitions." Electricalebook.com - Online Guide for Electrical Industry. Web. 29 Apr. 2010. .//
11. "Glossary." Home. Web. 29 Apr. 2010. ..
12. "Wetting." Wikipedia, the Free Encyclopedia. Web. 29 May 2010. .
13. "Chemical Bonds." Test Page for Apache Installation//. Web. 29 Apr. 2010. .